The AIDS epidemic has focused considerable attention on the risks associated with blood transfusions. Perhaps of more importance, hemolytic transfusion reactions and post-transfusion non-A non-B hepatitis continue to be significant concerns. However, guidelines for blood transfusions in the surgical patient vary considerably in the medical literature. Some recent texts stress the need to consider factors such as the patient's age, surgical procedure, co-morbid illness, predicted blood loss, and cause of the anemia, as well as the hemoglobin level. Nonetheless, in practice many surgeons still adhere to the 10g/dl threshold for transfusion. The lack of consensus guidelines can probably be attributed to the dearth of studies exploring the indications for transfusion. The few studies which have examined this question are limited because they fail to analyze subsets of patients by age, co-morbid illness, blood loss, etc. The need to develop peri-operative transfusions guidelines based on multivariate analysis, therefore decreasing the frequency of unnecessary transfusions resulting from the common use of a hemoglobin threshold, is especially important in light of the hazards and costs associated with blood transfusions. The FIST AWARD proposal is designed to meet this need. The goals of the proposed study are to 1) estimate the risk of death for patients with different pre-and post-operative hemoglobin levels and 2) to derive a multivariate model using clinical information available pre-operatively that would predict the risk of death post-operatively. The study population will consists of a population of 5000 Jehovah's Witness patients who decline blood transfusion for religious reasons. A case-control design will be used to explore possible associations between peri-operative anemia and post-operative mortality status. Cases will be defined as those who die within 30 days of the operative procedure, and controls as all those who survived. Three indicates of perioperative anemia will be considered: the hemoglobin value obtained just before surgery, the operative blood loss, and the lowest post-operative hemoglobin level. The case-control distributions of peri-objective anemia and other potential risk factors will be described. Odds ratios for post-operative death will be computed by comparing patients with normal hemoglobin levels to those with different levels of peri-operative anemia. Stratification and logistic regression will be used to control for the effects of confounding variables. Stepwise logistic regression will then be used to develop a clinical prediction rule. The model will be developed using a 66% random sample of the study population an validated on the remaining third.